1. Field of the Invention
The present invention relates to vibration and positioning of a light scanning apparatus in an image forming apparatus.
2. Description of the Related Art
In general, each component such as a light scanning apparatus, a photosensitive drum, a developing device, or a fixing device in an image forming apparatus is mounted on a support member such as a stay, and is mounted, together with the support member, on two side plates provided in the image forming apparatus in a state of being mounted on the support member. In such a configuration, a vibration generated by motor driving or engagements of gears of the photosensitive drum, the developing device, or the fixing device is transmitted through the side plates and the stay, finally to the light scanning apparatus. As a result, the light scanning apparatus itself or an optical component provided in the light scanning apparatus is forcedly vibrated. If the frequency of the transmitted vibration is close to the natural frequency of the light scanning apparatus itself or the optical component provided in the light scanning apparatus, the light scanning apparatus itself or the optical component provided in the light scanning apparatus resonates. This leads to a change in a laser irradiation position of a laser light emitted from the light scanning apparatus to the photosensitive drum, causing a defective image. Therefore, it is desired to reduce the vibration transmitted to the light scanning apparatus.
As a countermeasure against the vibration, a scanning optical apparatus disclosed in Japanese Patent Application Laid-Open No. 2007-25052 reduces a vibration of the scanning optical apparatus generated when a rotational polygon mirror in the scanning optical apparatus rotates, by mounting the scanning optical apparatus on an image forming apparatus via a viscoelastic member. On the other hand, an image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-98441 employs a structure in which a laser scanner is mounted on a scanner supporting component via an anti-vibration member so that the laser scanner is coupled to the scanner supporting component together with the anti-vibration member by using an adjustment screw. This structure reduces a vibration that is transmitted from various drive sources in the image forming apparatus to the laser scanner.
However, the scanning optical apparatus disclosed in Japanese Patent Application Laid-Open No. 2007-25052 has a structure in which the scanning optical apparatus mounted on a frame mounting portion via the viscoelastic member is fixed by being pressed in a direction of gravity by a fixing spring. Therefore, the scanning optical apparatus is supported by the elastic members from above and from below, and hence the elastic member reduces the vibration transmitted to the scanning optical apparatus. However, positioning in the direction of gravity may not be achieved to a sufficient level. As a result, it may be difficult to guarantee a laser beam scanning position on a surface of a photosensitive drum.
In addition, in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-98441, although positioning in the direction of gravity can be achieved by adjusting a tightening amount of the adjustment screw, the laser scanner and the scanner supporting component are integrated by the adjustment screw and thus vibrate together, weakening the anti-vibration effect obtained by interposing the anti-vibration member between the laser scanner and the scanner supporting component. Further, although the anti-vibration member is interposed between the laser scanner and the scanner supporting component, there is a possibility that the adjustment screw becomes another path for transmitting the vibration, and the vibration is transmitted from the scanner supporting component to the laser scanner.